Modeling of single- and multimode photonic-crystal planar waveguides with the plane-wave admittance method

In this paper we present the plane-wave admittance method (PWAM) in application to modeling light propagation in photonic crystal waveguides. We determine out-of-plane losses in single- and multimode waveguides and analyze the coupling of fundamental and higher-order modes in the latter case. Finally we compute the group velocity of light and show the possibilities and costs of achieving a very slow light regime.